Counting biological agents on biological growth plates

ABSTRACT

The invention is directed to counting techniques for counting biological agents on a biological growth plate or similar medium. In order to automate the counting of biological agents, a biological growth plate is inserted into a biological scanning unit. Upon insertion of the biological growth plate, the biological scanning unit generates an image of the plate. Then, the amount of biological agents that appear in the image, such as a number of bacteria colonies, can be counted or otherwise determined using image processing and analysis routines performed either by the scanning unit or an external computing device, such as a desktop computer, workstation or the like. A variety of counting rules are described herein that can be used to improve the accuracy of automated counts of biological agents on a biological growth plate.

FIELD

The invention relates to biological scaning systems for analysis ofbiological growth plates and detection of bacteria or other biologicalagents in food samples, laboratory samples, and the like.

BACKGROUND

Biological safety is a paramount concern in modem society. Testing forbiological contamination in foods or other materials has become animportant and often mandatory requirement for developers anddistributors of food products. Biological testing is also used toidentify bacteria or other agents in laboratory samples such as bloodsamples taken from medical patients, laboratory samples developed forexperimental purposes, and other types of biological samples. Varioustechniques and devices can be utilized to improve biological testing andto streamline and standardize the biological testing process.

A wide variety of biological growth plates have been developed. As oneexample, biological growth plates have been developed by 3M Company(hereafter “3M”) of St. Paul, Minn. In particular, biological growthplates are sold by 3M under the trade name PETRIFILM plates. Biologicalgrowth plates can be utilized to facilitate the rapid growth anddetection of bacteria or other biological agents commonly associatedwith food contamination, including, for example, aerobic bacteria, E.coli, coliform, enterobacteriaceae, yeast, mold, Staphylococcus aureus,Listeria, Campylobacter, and the like. The use of PETRIFILM plates, orother growth media, can simplify bacterial testing of food samples.

Biological growth plates can be used to enumerate or identify thepresence of bacteria so that corrective measures can be performed (inthe case of food testing) or proper diagnosis can be made (in the caseof medical use). In other applications, biological growth plates may beused to rapidly grow bacteria or other biological agents in laboratorysamples, e.g., for experimental purposes.

Biological scanning units refer to devices used to scan or countbacterial colonies, or the amount of a particular biological agent on abiological growth plate, or the like. For example, a food sample orlaboratory sample can be placed on a biological growth plate, and thenthe plate can be inserted into an incubation chamber. After incubation,the biological growth plate can be placed into the biological scanningunit for automated detection and enumeration of bacterial growth. Inthis manner, biological scanning units automate the detection andenumeration of bacteria or other biological agents on a biologicalgrowth plate, and thereby improve the biological testing process byreducing human error.

SUMMARY

In general, the invention is directed to techniques for countingbiological agents on a biological growth plate or similar medium. Tocount biological agents, a biological growth plate is inserted into abiological scanning unit. Upon insertion of the biological growth plate,the biological scanning unit generates an image of the plate. Then, theamount of biological agents that appear in the image, such as a numberof bacteria colonies, can be counted or otherwise determined using imageprocessing and analysis routines performed either within the biologicalscanning unit or by an external computing device, such as a desktopcomputer, workstation or the like. In accordance with the invention, avariety of counting rules are described that can be used to improve theaccuracy of automated counts of biological agents on a biological growthplate.

In one embodiment, the invention provides a method comprising receivingone or more images of a biological growth medium, determining whether abackground color value associated with the biological growth medium iswithin a range, and flagging the biological growth medium for additionalreview if the background color value is outside the range.

In another embodiment, the invention provides a method comprisingreceiving one or more images of a biological growth medium, identifyinga first count of biological agents on the biological growth medium, andreducing the first count to generate a second count when one or morebiological agents identified in the first count are determined to be inclose proximity to one or more other biological agents identified in thefirst count.

In another embodiment, the invention provides a method comprisingreceiving one or more images of a biological growth medium, identifyinga first number of biological agents associated with an interior portionof the biological growth medium, identifying a second number ofbiological agents associated with a perimeter portion of the biologicalgrowth medium, and excluding from the second number one or morebiological agents within a defined distance from an edge of a growtharea of the growth medium when the first number is less than athreshold.

In another embodiment, the invention provides a method comprisingreceiving one or more images of a biological growth medium, identifyinga number of first color biological agents associated with an interiorportion of the biological growth medium, identifying a number of secondcolor biological agents associated with the interior portion of thebiological growth medium, identifying a number of first color biologicalagents associated with a perimeter portion of the biological growthmedium, and identifying a number of second color biological agentsassociated with the perimeter portion of the biological growth medium.The method also includes changing the a number of second colorbiological agents associated with the perimeter portion to be includedin the number of first color biological agents associated with theperimeter portion when the number of first color biological agentsassociated with the interior portion is greater than a first thresholdand the number of second color biological agents associated with theinterior portion is less than a second threshold.

In another embodiment, the invention provides a method comprisingreceiving one or more images of a biological growth medium, identifyinga first number of biological agents associated with an interior portionof the biological growth medium, identifying a second number biologicalagents associated with a perimeter portion of the biological growthmedium, and flagging the biological growth medium for additional reviewif the second number is greater than a factor multiplied by the firstnumber.

In another embodiment, the invention provides computer readable mediumcomprising computer readable instructions that when executed in aprocessor receive one or more images of a biological growth medium,determine whether a background color value associated with thebiological growth medium is within a range, and flag the biologicalgrowth medium for additional review if the background color value isoutside the range.

In another embodiment, the invention provides a computer readable mediumcomprising computer readable instructions that when executed in aprocessor receive one or more images of a biological growth medium,identify a first count of biological agents on the biological growthmedium, and reduce the first count to generate a second count when oneor more biological agents identified in the first count are determinedto be in close proximity to one or more other biological agentsidentified in the first count.

In another embodiment, the invention provides a computer readable mediumcomprising computer readable instructions that when executed in aprocessor receive one or more images of a biological growth medium,identify a first number of biological agents associated with an interiorportion of the biological growth medium, identify a second number ofbiological agents associated with a perimeter portion of the biologicalgrowth medium, and exclude from the second number one or more biologicalagents within a defined distance from an edge of a growth area of thegrowth medium when the first number is less than a threshold.

In another embodiment, the invention provides a computer readable mediumcomprising computer readable instructions that when executed in aprocessor receive one or more images of a biological growth medium,identify a number of first color biological agents associated with aninterior portion of the biological growth medium, identify a number ofsecond color biological agents associated with the interior portion ofthe biological growth medium, identify a number of first colorbiological agents associated with a perimeter portion of the biologicalgrowth medium, identify a number of second color biological agentsassociated with the perimeter portion of the biological growth medium,and change the a number of second color biological agents associatedwith the perimeter portion to be included in the number of first colorbiological agents associated with the perimeter portion when the numberof first color biological agents associated with the interior portion isgreater than a first threshold and the number of second color biologicalagents associated with the interior portion is less than a secondthreshold.

In another embodiment, the invention provides a computer readable mediumcomprising computer readable instructions that when executed in aprocessor receive one or more images of a biological growth medium,identify a first number of biological agents associated with an interiorportion of the biological growth medium, identify a second numberbiological agents associated with a perimeter portion of the biologicalgrowth medium, and flag the biological growth medium for additionalreview if the second number is greater than a factor multiplied by thefirst number.

In another embodiment, the invention provides a system comprising animaging device to generate one or more images of a biological growthmedium, and a processor to receive the images, determine whether abackground color value associated with the biological growth medium iswithin a range, and flag the biological growth medium for additionalreview if the background color value is outside the range.

In another embodiment, the invention provides a system comprising animaging device to generate one or more images of a biological growthmedium, and a processor to receive the images, identify a first count ofbiological agents on the biological growth medium, and reduce the firstcount to generate a second count when one or more biological agentsidentified in the first count are determined to be in close proximity toone or more other biological agents identified in the first count.

In another embodiment, the invention provides a system comprising animaging device to generate one or more images of a biological growthmedium, and a processor to receive the images, identify a first numberof biological agents associated with an interior portion of thebiological growth medium, identify a second number of biological agentsassociated with a perimeter portion of the biological growth medium, andexclude from the second number one or more biological agents within adefined distance from an edge of a growth area of the growth medium whenthe first number is less than a threshold.

In another embodiment, the invention provides a system comprising animaging device to generate one or more images of a biological growthmedium, and a processor to receive the images, identify a number offirst color biological agents associated with an interior portion of thebiological growth medium, identify a number of second color biologicalagents associated with the interior portion of the biological growthmedium, identify a number of first color biological agents associatedwith a perimeter portion of the biological growth medium, identify anumber of second color biological agents associated with the perimeterportion of the biological growth medium, and change the a number ofsecond color biological agents associated with the perimeter portion tobe included in the number of first color biological agents associatedwith the perimeter portion when the number of first color biologicalagents associated with the interior portion is greater than a firstthreshold and the number of second color biological agents associatedwith the interior portion is less than a second threshold.

In another embodiment, the invention provides system comprising animaging device to generate one or more images of a biological growthmedium, and a processor to receive the images, identify a first numberof biological agents associated with an interior portion of thebiological growth medium, identify a second number biological agentsassociated with a perimeter portion of the biological growth medium, andflag the biological growth medium for additional review if the secondnumber is greater than a factor multiplied by the first number.

Various aspects of the invention may provide a number of advantages. Forexample, the invention may improve the accuracy of automated counts ofbiological agents on a biological growth plate. In particular, the rulesdescribed herein may address problems that commonly occur, and which canotherwise undermine the accuracy of automated counting of agents on agrowth plate.

In addition, the invention may reduce costs of a biological system byallowing lower cost optical elements to be used in an imaging device.For example, one or more of the counting rules described herein maycompensate for optical defects in an imaging device. Accordingly, insome cases counting rules can reduce the costs of a system biologicalscanning system by allowing lower cost optical elements to be used inthe imaging device.

Additional details of these and other embodiments are set forth in theaccompanying drawings and the description below. Other features, objectsand advantages will become apparent from the description and drawings,and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a biological scanning system that canexecute counting techniques in accordance with the invention.

FIG. 2 is a perspective view of another exemplary biological scanningsystem comprising a scanning unit coupled to an external computer whichperforms imaging analysis as described herein.

FIG. 3 is a block diagram of a biological scanning system that maycorrespond to either of the systems illustrated in FIG. 1 or FIG. 2.

FIG. 4 is a flow diagram illustrating a process of automated biologicalgrowth plate analysis.

FIGS. 5 and 6 are diagrams of exemplary growth media collectivelyillustrating one problem that can occur.

FIG. 7 is a flow diagram illustrating a rule 1 that may be used during aprocess of automated biological growth plate analysis to address theproblem illustrated in FIGS. 5 and 6.

FIG. 8 is a diagram of an exemplary growth medium illustrating oneproblem that can occur.

FIG. 9 is a flow diagram illustrating a rule 2A that may be used duringa process of automated biological growth plate analysis to address theproblem illustrated in FIG. 8.

FIG. 10 is a flow diagram illustrating a rule 2B that may be used duringa process of automated biological growth plate analysis to address theproblem illustrated in FIG. 8.

FIG. 11 is a diagram of an exemplary growth medium illustrating oneproblem that can occur.

FIG. 12 is a flow diagram illustrating a rule 3A that may be used duringa process of automated biological growth plate analysis to address theproblem illustrated in FIG. 11.

FIG. 13 is a flow diagram illustrating a rule 3B that may be used duringa process of automated biological growth plate analysis to address theproblem illustrated in FIG. 11.

FIG. 14 is a diagram of an exemplary growth medium illustrating oneproblem that can occur.

FIG. 15 is a flow diagram illustrating a rule 4 that may be used duringa process of automated biological growth plate analysis to address theproblem illustrated in FIG. 14.

FIG. 16 is a diagram of an exemplary growth medium illustrating oneproblem that can occur.

FIG. 17 is a flow diagram illustrating a rule 5 that may be used duringa process of automated biological growth plate analysis to address theproblem illustrated in FIG. 16.

FIG. 18 is a diagram of an exemplary growth medium illustrating oneproblem that can occur.

FIG. 19 is a flow diagram illustrating a rule 6 that may be used duringa process of automated biological growth plate analysis to address theproblem illustrated in FIG. 18.

DETAILED DESCRIPTION

The invention is directed to techniques for counting biological agentson a biological growth plate or similar medium. A variety of countingrules are described in greater detail below that can be used to improvethe accuracy of automated counts of biological agents on a biologicalgrowth plate. The counting rules are typically stored ascomputer-executable software instructions, and are executed by aprocessor in a biological scanning system. Alternatively, the rules maybe implemented in hardware such as an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA), or varioushardware components. The various rules described herein may be appliedindividually, or in any combination depending on the growth medium beingscanned. In any case, by applying one or more of the rules describedherein, the accuracy of automated counts of biological agents on abiological growth plate can be improved.

FIG. 1 is a perspective view of an exemplary biological scanning system10 capable of implementing the counting rules described herein. As shownin FIG. 1, biological scanning system 10 includes a scanning unit 12having a drawer 14 that opens to receive a biological growth plate (notshown in FIG. 1). Drawer 14 moves the biological growth plate intoscanning unit 12 for scanning and analysis. An imaging device and aprocessor reside within scanning unit 12. When a biological growth plateis inserted into scanning unit 12 via drawer 14, the imaging devicegenerates one or more images of the growth plate. The images are thensent to the processor, which counts the number of biological agents onthe growth medium via image analysis. In particular, the processorwithin scanning unit 12 invokes one or more counting rules, as describedin greater detail below, that can be used to improve the accuracy ofautomated counts of biological agents on a biological growth plate.

Biological scanning system 10 also may include a display screen 16disposed on scanning unit 12 to display the progress or results ofanalysis of the biological growth plate to a user. Alternatively oradditionally, display screen 16 may present to a user an image of thegrowth plate scanned by scanning system 10. The displayed image may beoptically magnified or digitally scaled upward. A mounting platform 18defines an ejection slot 20 through which the growth plate can beejected following image capture by biological scanning system 10. Inother words, biological scanning system 10 may have a two-part design inwhich scanning unit 12 is mounted on mounting platform 18. The two-partdesign is depicted in FIG. 1 for purposes of example, and is notintended to be required by or limiting of the inventions describedherein.

Scanning unit 12 houses an imaging device for scanning the biologicalgrowth plate and generating an image. The imaging device may take theform of a line scanner or an area scanner, which ordinarily operates incombination with an illumination system to provide front and/or backillumination of the biological growth plate. In addition, scanning unit12 may house processing hardware, software and/or firmware that performsanalysis of the scanned image, e.g., in order to determine the number oramount of biological agents on the growth plate. For example, uponpresentation of the biological growth plate via drawer 14, the plate maybe positioned adjacent an optical platen for scanning. Again, inaccordance with the invention, various counting rules can be applied bya processor within scanning unit 12 in order to improve the accuracy ofautomated counts of biological agents on a biological growth plate.

When drawer 14 is opened following the scan of a growth plate, thegrowth plate may drop downward into the mounting platform 18 forejection via ejection slot 20. To that end, mounting platform 18 mayhouse a conveyor that ejects the growth plate from scanning unit 12 viaejection slot 20. In other words, after a biological growth plate isinserted into drawer 14, moved into scanning unit 12, and scanned, thebiological growth plate drops downward into mounting platform 18, wherea horizontal conveyor, such as a moving belt, ejects the medium via slot20.

FIG. 2 is a perspective view of another biological scanning system 20capable of implementing the counting rules described herein. Biologicalscanning system 20 comprises a scanning unit 21 coupled to an externalcomputer 22 which performs imaging analysis of the images generated byscanning unit 21. In other words, whereas system 10 (FIG. 1) integratesa processor internally inside scanning unit 12, system 20 (FIG. 2) makesuse of a processor external to scanning unit 21, e.g., in externalcomputer 22. For example, external computer 22 may include amicroprocessor that executes software for image analysis of biologicalgrowth plate 24. External computer 22 may comprise a personal computer(PC), desktop computer, laptop computer, handheld computer, workstation,or the like. For example, software programs can be loaded on externalcomputer 22 to facilitate image analysis of images of biological growthplate 24 generated by biological scanning system 20.

Scanning unit 21 is coupled to external computer 22 via interface 25.Interface 25, for example, may comprise a Universal Serial Bus (USB)interface, a Universal Serial Bus 2 (USB2) interface, an IEEE 1394FireWire interface, a Small Computer System Interface (SCSI) interface,an Advance Technology Attachment (ATA) interface, a serial ATAinterface, a Peripheral Component Interconnect (PCI) interface, aconventional serial or parallel interface, or the like.

As illustrated, biological scanning system 20 is designed to receive abiological growth plate 24. In particular, scanning unit 21 includes ahousing 26 that defines an input slot 28 for receiving biological growthplate 24. A guide mechanism 23 may be formed on housing 26 to aidinsertion of biological growth plate 24 into scanning unit 21. Scanningunit 21 also includes an ejection slot (not shown), through which growthplate 24 is ejected following imaging of growth plate 24. Scanning unit21may also include other features, such as a display screen (not shown)to display the progress or results of analysis of the biological growthplate to a user.

Scanning unit 21 houses an imaging device, such as a 2-dimensionalmonochromatic camera for generating one or more images of an insertedbiological growth plate 24. In addition, scanning unit 21 may housevarious illuminators for illuminating the front and back of biologicalgrowth plate 24 during imaging. The illuminators can illuminatebiological growth plate 24 with one or more colors, and one or moreimages of growth plate 24 can be generated and then analyzed todetermine bacteria counts on growth plate 24. In particular scanningunit 21 communicates the images to external computer 22, which includesa processor for performing image analysis.

Growth plate 24 may include a growth area 27 where bacteria or otheragents manifest on growth plate 24. Growth area 27 may be a flat surfaceor a recessed well. A determination of whether a given sample beingtested in growth plate 24 is acceptable, in terms of bacterial colonycounts, may depend on the number of bacterial colonies per unit area.Accordingly, images generated by scanning unit 21 can be used toquantify the amount of bacterial colonies per unit area on plate 24. Thesize of individual colonies may also be factored into the analysis, ifdesired. The surface of biological growth plate 24 in growth area 27 maycontain one or more growth enhancing agents designed to facilitate therapid growth of one or more types of bacteria or other biologicalagents. In some cases, biological growth plate 24 is incubated prior toinsertion into scanning unit 21.

Growth plate 24 may also include indicia 29, such as a bar code or othertype of identification marking used to identify growth plate 24. RFIDtags, two-dimensional optically detectable codes, or the like, may alsobe used as indicia. In any case, indicia 29 may identify the type ofbacteria or biological agent being grown and tested on growth plate 24.Scanning unit 21 can be designed to draw growth plate 24 into scanningunit 21 to a first location and generate an image of indicia 29, andthen draw growth plate 24 to a second location and generate an image ofgrowth area 27. In this manner, images of indicia 29 and growth area 27can be generated by biological scanning system 20. Alternatively, asingle image may capture both indicia 29 and the growth area 27. Ineither case, the scanning of indicia 29 can facilitate identification ofthe type of plate being used so that one or more desirable countingrules can be applied in an automated fashion.

By way of example, growth plate 24 may comprise a biological growthplate sold by 3M under the trade name PETRIFILM plates. Growth plate 24can be utilized to facilitate the rapid growth and detection of bacteriaor other biological agents commonly associated with food contamination,including, for example, aerobic bacteria, E. coli, coliform,enterobacteriaceae, yeast, mold, Staphylococcus aureus, Listeria,Campylobacter, or the like. Growth plates are generally one type ofgrowth medium commonly used for biological growth and bacterialdetection and enumeration. The invention, however, may also be appliedwith a wide variety of other types of growth media.

In order to improve the accuracy of automated counts of biologicalagents on a biological growth plate, various aspects of the inventionestablish rules that can be applied during image processing. In otherwords, the rules described in greater detail below can form part of acounting algorithm executed in system 10 or system 20. The differentrules may be used individually or in any combination, depending on thetype of growth medium being scanned and the problems that may beencountered. For example, some rules may be relevant for particulartypes of growth plates as outlined below. The order in which rules areapplied may also affect the result. In any event, application of one ormore of the counting rules can improve a biological scanning system suchas system 10 or system 20 by improving the accuracy of automated countsof biological agents on a growth medium such as a growth plate or thelike.

FIG. 3 is a block diagram of a biological scanning system 30, which maycorrespond to system 10 (FIG. 1) or system 20 (FIG. 2). Biologicalscanning system 30 includes an imaging device 32 that generates one ormore images of a growth medium and provides the images to processor 34.Processor 34 is coupled to memory 36. Memory 36 stores variousprocessor-executable software instructions that facilitate imageanalysis of the images generated by imaging device 32. In particular,memory 36 stores one or more counting rules 37 which are applied duringimage analysis to improve the accuracy of automated counts of biologicalagents on a biological growth plate. Output device 38 receives theresults determined by processor 34 and provides the results to a user.

By way of example, imaging device 32 may comprise a 2-dimensionalmonochromatic camera for generating one or more images of a biologicalgrowth plate. Various illuminators (not shown) may be used to illuminatethe front and back of biological growth plate. For example, theilluminators can illuminate the biological growth plate with one or morecolors, and one or more images of the growth plate can be generated byimaging device 32. The images are provided to processor 34 and may alsobe stored in memory 36. In any case, the images are analyzed by applyingcounting rules 37 in order to determine bacteria counts on the growthplate. The resolution of imaging device 32 may be approximately 155pixels per centimeter. In that case, a one centimeter line in the imageis 155 pixels long and each pixel is

Reducing the cost of imaging device 32 is desirable. Although high costoptical elements, such as high-quality lenses can improve imaging, suchelements can drive up the cost of system 30 to exorbitant levels. One ormore of counting rules 37 may provide an alternative mechanism forachieving improvements in system 30. For example, one or more countingrules 37 may compensate for optical defects in imaging device 32.Accordingly, in some cases, counting rules 37 can reduce the costs ofsystem 30 by allowing lower cost optical elements to be used in imagingdevice 32.

Processor 34 may comprise a general-purpose microprocessor that executessoftware stored in memory 36. Alternatively, processor 34 may comprisean application specific integrated circuit (ASIC) or other specificallydesigned processor. In any case, processor 34 executes various countingrules 37 to improve the accuracy of automated counts of biologicalagents on a biological growth plate.

Memory 36 is one example, of a computer readable medium that storesprocessor executable software instructions applied by processor 34. Byway of example, memory 36 may comprise random access memory (RAM),read-only memory (ROM), non-volatile random access memory (NVRAM),electrically erasable programmable read-only memory (EEPROM), flashmemory, or the like. Counting rules 37 such as those described below,are stored in memory 36 and may form part of a larger software programused for image analysis.

Output device 38 typically comprises a display screen used tocommunicate results to a user. However, output device 38 could alsocomprise other types of devices such as a printer or the like. Outputdevice 38 may form part of a biological scanning unit, such as display16 of scanning unit 12 (FIG. 1), or may be external to the scanningunit, such as the display screen of external computer 22 (FIG. 2).

FIG. 4 is a flow diagram illustrating a process of automated biologicalgrowth plate analysis. As shown in FIG. 4, processor 34 receives one ormore images of a growth plate (41). Processor 34 invokes varioussoftware routines from memory 36 to count the biological agents on thegrowth plate (42). For example, bacterial colonies may be identifiedaccording to color differences, in which bacterial colonies manifest onthe growth medium by changing color. The software executed by processor34 can allow for identification of the biological growth area on thegrowth plate and automated counting of bacterial colonies based on colorchanges in the growth area where the colonies have grown duringincubation.

In accordance with the invention, processor 34 applies one or more rulesto improve the accuracy of the count of biological agents on the growthmedium (43). A variety of rules are described in the followingdescription. The rules may be applied individually or variouscombinations of rules may be used, depending on the type of growth platebeing analyzed. The rules may be individually invoked from memory 36 ormay form sub-routines of a larger image analysis software program. Therules described below are labeled as rules 1, 2A, 2B, 3A, 3B, 4, 5 and6. This notation, however, is provided to aid the discussion of therules, and in no way implies an order of the application of the rules.The rules may be applied individually or various sets of the rules maybe applied. If a set of rules are used, then the order in which therules are applied may be selected based on the type of plate beingscanned. The selected order for application of the rules may affect theend result. Various subsets of the rules may also be applied in anyorder, and the selected order for a subset of rules may also affect theend result.

FIG. 5 illustrates an exemplary growth plate 50 including a growth area52 and indicia 54, e.g., for identifying plate 50 as a specific type ofgrowth plate, sample dilution, sample type or origin. Similarly, FIG. 6illustrates an exemplary growth plate 60 including a growth area 62 andindicia 64. As illustrated, the background color or shading associatedwith growth area 52 of growth plate 50 is different than that of growtharea 62 of growth plate 60. If the background color associated withgrowth area 52 of growth plate 50 does not fall within a defined colorrange, then problems may exist with respect to growth plate 50. Inaccordance with rule 1 described herein, the color of a growth plate canbe identified and compared to a color range. If the color of the growthplate falls outside the range, the growth plate can be flagged forreview by a technician.

FIG. 7 is a flow diagram illustrating rule 1. As illustrated, processor34 invokes software stored in memory 36 to identify the color value of agrowth plate (71). In particular, processor 34 may quantify the color ofthe growth plate as one or more numeral values that defines the shade ofthe plate. The shade, for example, may be characterized by 3 numbersdefining red, green and blue values, or hue, saturation and intensityvalues. If one or more of the color values of the growth plate areoutside a rule 1 range (72), e.g., if the shade of the plate is notwithin a range of shades established as acceptable, then that growthplate is flagged for additional review (73). For example, flagged growthplates may require technician review in order to determine if the colorof the growth plate indicates a problem. In this manner, rule 1automates the identification of potentially faulty growth plates basedon the color of the plate. The rule 1 color range is generally specificto the type of growth plate used, and generally establishes a range ofcolors that indicate that the growth plate is acceptable. Shade valuescan be used to define the color range and color values with one or morenumerical values.

FIG. 8 illustrates an exemplary growth plate 80 including a growth area82 and indicia 84. FIG. 8 also provides a legend which indicates thatsquare-shaped areas are colonies that have been identified andcircular-shaped areas are colonies with gas that have been identified.For some growth plates, colonies with gas indicate confirmed types ofbiological colonies that can be enumerated, whereas colonies without gasindicate a colony that may or may not be enumerated.

One problem with growth plates is that one colony may split andgenerally manifest as two or more distinct marks on the growth plate. Inthat case, the two or more distinct marks generally indicate the samecolony for purposes of bacterial counts. However, automated systems maycount each marking as a separate colony. This problem often becomes moreprevalent with colonies that include gas because the gas may generatefrom within, above or below the perimeter of the colony, which canaffect the colony and cause it to split.

In order to reduce this problem, rules 2A and 2B provide alternativetechniques for identifying colonies that have likely split from a singlecolony that grew on the growth plate. In general, when a growth plateincludes a limited number of colonies and two or more colonies are veryclose together, it may be desirable to count the two or more coloniesthat are very close together as a single colony because of a highprobability that the two colonies split from a single colony that grewon the growth plate. The sets of colonies identified at 85A, 85B and85C, for example, may be likely candidates for application of such arule.

FIG. 9 is a flow diagram illustrating rule 2A. Processor 34 invokessoftware stored in memory 36 to analyze one or more images of abiological growth plate count the number of biological agents on theplate. If the plate count, i.e., the initial number of agents identifiedon the plate is greater than a rule 2 threshold (no branch of 91), thenno change is made to the plate count. However, if the plate count isless than the rule 2 threshold (yes branch of 91), then changes mayoccur. For example, the rule 2 threshold may be approximately 20although this number could take any value for various implementations.In general, it is most desirable to invoke steps (92-94) when the numberof initial counts is relatively small because incorrect counts have amore drastic affect on the percentage of counts when the number of totalcounts is relatively low.

If the plate count is less than the rule 2 threshold (yes branch of 91),then processor 34 determines whether one colony is within a defineddistance D₂ of another colony (92). If so (yes branch of 92), processorattributes only one count to the two colonies within the defineddistance D₂ of each other (73). The distance D₂ may be defined in termsof absolute distance or in terms of pixels in the images. For example,the distance D₂ may be defined as a width of approximately 18 pixelsfrom center to center of two pixels. If two colonies are within distanceD₂ of each other (93), e.g., from center to center, those two coloniesare counted as one colony.

In other words, if two colonies are very close to one another on agrowth plate that has relatively few colonies, then those two coloniesare counted as a single colony because of a high probability that thetwo colonies split from a single colony that grew on the growth plate.Processor 34 considers every colony on the growth plate and determinesfor each colony whether it has neighboring colonies within the distanceD₂ of the given colony. The process of rule 2A ends when there are nomore colonies to consider (no branch of 94). Accordingly, if three ormore colonies are within a distance D₂ of one another, the three or morecolonies will be counted as one colony.

FIG. 10 is a flow diagram illustrating rule 2B, which is a slightvariation to rule 2A. Rules 2A and 2B are generally alternatives ofsolving a similar problem, e.g., identifying when two or more coloniesin an initial count should be counted as a single colony. In both cases,processor 34 generates a first count, and then reduces the first countto generate a second count upon identifying two or more colonies in thefirst count that should be counted as a single colony. The same rule 2threshold X₂ is used in FIG. 9 and 10, although different thresholdscould also be used for the different rules.

Again, processor 34 invokes software stored in memory 36 to analyze oneor more images of a biological growth plate count the number ofbiological agents on the plate. If the plate count, i.e., the initialnumber of agents identified on the plate is greater than a rule 2threshold (no branch of 101), then no change is made to the plate count.However, if the plate count is less than the rule 2 threshold (yesbranch of 101), then changes may occur.

In particular, if the plate count is less than the rule 2 threshold (yesbranch of 101), then processor 34 determines whether two coloniesoverlap (102). For example, processor 34 may define an identificationmark that surrounds an area associated with each colony, which istypically between approximately 0.2 and 0.3 centimeters in diameter,although the colony mark may be proportional to the size of the colonyexhibited. If two identification marks of two different areas overlap(yes branch of 102), processor 34 attributes only one count to the twocolonies that overlap (103). In other words, if two colonies are veryclose to one another on a growth plate that has relatively few colonies,then those two colonies are counted as a single colony because of a highprobability that the two colonies split from a single colony that grewon the growth plate. Processor 34 considers every colony on the growthplate and determines for each colony whether it has neighboring coloniesthat overlap with the given colony. The process of rule 2B ends whenthere are no more colonies to consider (no branch of 104).

FIG. 11 illustrates an exemplary growth plate 110 including a growtharea 112 and indicia 114. FIG. 11 also provides a legend which indicatesthat circular-shaped areas are colonies, and relatively large irregularshapes are spreader colonies (also referred to as “liquefier colonies”).One problem with growth plates like that illustrated in FIG. 11 is thatone or more colonies may manifest from a spreader colony. In that case,the colonies that are relatively close to a spreader colony may actuallybe part of the spreader colony and not a separate and distinct colony.However, automated systems may count each marking as a separate colony,including the spreader colony and various colonies that manifest fromthe spreader colony.

In order to reduce this problem, rules 3A and 3B provide alternativetechniques for identifying colonies that have likely split from aspreader colony. Rules 3A and 3B are very similar to rules 2A and 2Bidentified above, but are specific to cases where spreader colonies havebeen identified. In general, when a growth plate includes a limitednumber of colonies and one or more colonies are very close to arelatively large spreader colony, it may be desirable to include the twoor more colonies that are very close to the spreader colony as part ofthe spreader colony. The spreader colonies identified at 115A and 115B,for example, may be likely candidates for application of such a rule.The same rule 3 threshold X₃ is used in FIGS. 12 and 13, althoughdifferent thresholds could also be used for the different rules.

FIG. 12 is a flow diagram illustrating rule 3A. Processor 34 invokessoftware stored in memory 36 to analyze one or more images of abiological growth plate count the number of biological agents on theplate. If the plate count, i.e., the initial number of agents identifiedon the plate is greater than a rule 3 threshold (no branch of 121), thenno change is made to the plate count. However, if the plate count isless than the rule 3 threshold (yes branch of 121), then changes mayoccur. For example, the rule 3 threshold may be approximately 150although this number could take any value for various implementations.In general, it is most desirable to invoke steps (122-123) when thenumber of initial counts is below a threshold because incorrect countshave a more drastic affect on the percentage of counts when the numberof total counts is relatively low.

If the plate count is less than the rule 3 threshold (yes branch of121), then processor 34 determines whether a spreader colony wasidentified (122). For example, spreader colonies may be identified basedon shape, size and/or color. In particular spreader colonies generallyhave a relatively large irregular shape and may manifest at a slightlydifferent color than other colonies. If one or more spreader coloniesare identified, then processor 34 excludes from the count, any colonieswithin a defined distance (D₃) of the spreader colony. The distance D₃may be defined in terms of absolute distance or in terms of pixels inthe images. For example, the distance D₃ may be approximately 0.065 cm,which may correspond to the width of approximately 10 pixels in system30. In any case, any colonies within distance D₃ of a spreader colonyare excluded from the count, and attributed to being part of thespreader colony.

FIG. 13 is a flow diagram illustrating rule 3B, which is a slightvariation to rule 3A. Rules 3A and 3B are generally alternatives ofsolving a similar problem, e.g., identifying when colonies in an initialcount should be counted as part of a spreader colony. In both cases,processor 34 generates a first count, and then reduces the first countto generate a second count upon identifying a spreader colony andanother colony that should be counted as part of the spreader colony.

Processor 34 invokes software stored in memory 36 to analyze one or moreimages of a biological growth plate count the number of biologicalagents on the plate. If the plate count, i.e., the initial number ofagents identified on the plate is greater than a rule 3 threshold (nobranch of 131), then no change is made to the plate count. However, ifthe plate count is less than the rule 3 threshold (yes branch of 131),then changes may occur.

In particular, if the plate count is less than the rule 3 threshold (yesbranch of 131), then processor 34 determines whether a spreader colonywas identified (132). Again, spreader colonies may be identified basedon shape, size and/or color. If one or more spreader colonies areidentified, then processor 34 excludes from the count, any colonies thatoverlap with spreader colony (133). For example, processor 34 may definea relatively large identification mark that surrounds an area associatedwith the spreader colony. In addition, processor 34 may defineidentification marks that surround areas associated with other colonies.If the identification mark associated with the spreader colony overlapsthat of any other colonies, the other colonies that overlap the spreadercolony are excluded from the count. In that case, the other coloniesthat overlap the spreader colony are attributed to being part of thespreader colony.

FIG. 14 illustrates an exemplary growth plate 140 including a growtharea 142 and indicia 144. FIG. 14 also provides a legend which indicatesthat square-shaped areas are colonies that have been identified andcircular-shaped areas are colonies with gas that have been identified.Different shading distinguishes “red” colonies from “blue colonies.” Ofcourse, the colors red and blue are exemplary, and similar growth platesmay use any other colors. In general, a first color may correspond toone type of colony and the second color may correspond to another typeof colony. In some cases, one color may identify a general colony andanother may identify a more specific colony. For example, red mayidentify a coliform colony and blue may identify an E. coli colony,which is a specific type of coliform. Colonies with gas may indicateconfirmed types of biological colonies that can be enumerated, whereascolonies without gas may indicate a colony that may or may not beenumerated with certainty, e.g., in accordance with governmentalregulations.

One problem with growth plate analysis is that imaging artifacts cancause irregularities in images of growth plates. If relatively low costoptical elements, such as low cost lenses, are used in the imagingdevice, this problem can be significant. On the other hand, however, itis desirable to control the costs in a biological scanning system andhigh cost optical elements can add considerable costs. Accordingly, abetter option to using higher cost optical elements may be thedevelopment of image analysis rules and techniques that can identify andovercome problems associated with lower cost optical elements.

Growth plate 140 includes a relatively few number of colonies in acenter portion 147 of growth area 142. However, a larger number ofcolonies are present in a perimeter portion 149 of growth area 142.Statistically, it is expected that the colonies will be evenlydistributed. Accordingly, when a much larger number of colonies arepresent in a perimeter portion 149 of growth area 142 than interiorportion, a problem may be identified. This phenomenon may be attributedto optical defects in imaging device 32. In the following description,the interior portion 147 generally refers to approximately the interiormost 75 percent of growth area 142, whereas perimeter portion 149 refersto approximately the perimeter most 25 percent of the growth area 142.In other embodiments, however, the perimeter portion and interiorportion may be allocated differently.

FIG. 15 is a flow diagram illustrating rule 4, which addresses theproblem illustrated in FIG. 14. Although FIG. 15 is described withreference to the colors “red” and “blue,” the rule may be applied moregenerally to any first and second colors.

Processor 34 invokes software stored in memory 36 to analyze one or moreimages of a biological growth plate count the number of biologicalagents on the plate. Processor 34 identifies a number of red counts(R_(interior)) in the interior portion of a biological growth plate,e.g. interior portion 147 (151). In addition, processor 34 identifies anumber of blue counts (B_(interior)) in the interior portion of abiological growth plate (152). If the number red counts (R_(interior))in the interior portion of a biological growth plate is less than a rule4 threshold (X₄) (yes branch of 153), then processor does not count anysmall area red colonies within a defined distance D₄ of the outer edgeof the growth plate, e.g., perimeter portion 149 (154). Similarly, ifthe number blue counts (B_(interior)) in the interior portion of abiological growth plate is less that a rule 4 threshold (X₄) (yes branchof 155), then processor does not count any small area blue colonieswithin a defined distance D₄ of the outer edge of the growth plate,e.g., perimeter portion 149 (154).

Small area colonies generally refer to colonies having a defined area ordiameter less than a defined threshold. The small area colonies may bedefined relative to an absolute measured size or may be defined in termsof pixels in the images. In one example, small area colonies arecolonies having a size smaller than approximately 20 pixels. Thedistance D₄ may be defined in terms of absolute distance or in terms ofpixels in the images. For example, the distance D₄ may be defined as thewidth of approximately 5 pixels.

FIG. 16 illustrates an exemplary growth plate 160 including a growtharea 162 and indicia 164. FIG. 16 also provides a legend which indicatesthat square-shaped areas are colonies that have been identified andcircular-shaped areas are colonies with gas that have been identified.Different shading distinguishes “red” colonies from “blue colonies.”Again, however, the colors red and blue are exemplary, and similargrowth plates may use any other colors. In general, a first color maycorrespond to one type of colony and the second color may correspond toanother type of colony. In some cases, one color may identify a generalcolony and another may identify a more specific colony. For example, redmay identify a coliform colony and blue may identify an E. coli colony,which is a specific type of coliform. Colonies with gas may indicateconfirmed types of biological colonies that can be enumerated, whereascolonies without gas may indicate a colony that may or may not beenumerated with certainty, e.g., in accordance with governmentalregulations.

One problem with growth plate analysis is that the growth plate mayexhibit an uneven triggering(chemical reaction) of growth indicators.Statistically, it is expected that the colonies will be evenlydistributed. If a much higher percentage of red colonies manifest in onearea and a much higher percentage of blue colonies manifest in anotherarea, a problem may be identified. In that case, the blue colonies maybe counted as red colonies, e.g., where the red colonies identify a moregeneral presence of bacterial growth and the blue colonies identify amore specific type of bacterial growth. With uneven distribution, thepresence of blue colonies are less reliable as indicators of thespecific type of bacterial growth, but would typically still indicatemore general bacterial presence. Accordingly, in automated bacterialcolony counting it may be desirable to count the blue colonies as redcolonies if uneven distribution is identified, particularly in plateshaving relatively low bacterial counts.

In growth plate 160 (FIG. 16) for example, six red colonies are presentin interior portion 167 and one red colony with gas is present ininterior portion 167. No blue colonies or blue colonies with gas arepresent in interior portion 167. In contrast, perimeter portion 169includes three blue colonies, one blue colony with gas, and one redcolony. In that case, the blue colonies and blue colonies with gas maybe counted as red colonies (where the blue with gas are optimallycounted as red with gas) because of the uneven distribution. Theinterior portion 167 may refer to approximately the interior most 75percent of growth area 162, whereas the perimeter portion 169 may referto approximately the perimeter most 25 percent of the growth area 162.In other embodiments, however, the perimeter portion and interiorportion may be allocated differently.

FIG. 17 is a flow diagram illustrating rule 5, which addresses theproblem illustrated in FIG. 16. Although FIG. 17 is described withreference to the colors “red” and “blue,” the rule may be applied moregenerally to any first and second colors.

Processor 34 invokes software stored in memory 36 to analyze one or moreimages of a biological growth plate count the number of biologicalagents on the plate. Processor 34 identifies a number of red counts(R_(interior)) in the interior portion of a biological growth plate,e.g. interior portion 167 (171). In addition, processor 34 identifies anumber of blue counts (B_(interior)) in the interior portion of thebiological growth plate (172). Also, processor 34 identifies a number ofred counts (R_(perimeter)) in the perimeter portion of the biologicalgrowth plate, e.g. perimeter portion 169 (173), and identifies a numberof blue counts (B_(perimeter)) in the perimeter portion of thebiological growth plate (174).

If the number of red counts (R_(interior)) in the interior portion isgreater than a first rule 5 threshold (X₅) and the number of blue counts(B_(interior)) in the interior portion is less than a second rule 5threshold (Y₅) (yes branch of 175), then processor 34 changes the bluecounts (B_(perimeter)) in the perimeter portion of the plate to redcounts (176). In other words, blue colonies in the perimeter portion arecounted as red colonies when uneven distribution is identified to anextent that defies probable statistics. By way of example, the firstrule 5 threshold (X₅) may be approximately five and the second rule 5threshold (Y₅) may be approximately two, although these numbers may beselected differently according to the desired implementation.

FIG. 18 illustrates an exemplary growth plate 180 including a growtharea 182 and indicia 184. FIG. 18 also provides a legend which indicatesthat square-shaped areas are colonies.

Again, one problem with growth plate analysis is that the growth platemay exhibit an uneven triggering(chemical reaction) of growthindicators. Statistically, it is expected that the colonies will beevenly distributed. If a much higher percentage of colonies manifest inone area than another area, a problem may be identified. In that case,it may be desirable to flag the growth plate for additional review,e.g., by a technician.

In growth plate 180 (FIG. 18) for example, four colonies are present ininterior portion 187. In contrast, perimeter portion 189 includesfifteen colonies. In that case, it may be desirable to flag the growthplate for additional review, e.g., by a technician because thedistribution of colonies defies probable statistics.

FIG. 19 is a flow diagram illustrating rule 6, which addresses theproblem illustrated in FIG. 18. Processor 34 invokes software stored inmemory 36 to analyze one or more images of a biological growth platecount the number of biological agents on the plate. Processor 34 makesan initial count over the growth area and determines whether the platecount is greater than a rule 6 threshold (X₆) (191). By way of example,the rule 6 threshold (X₆) may be approximately five, although othervalues could be used in other implementations.

If the plate count is greater than a rule 6 threshold (X₆) (yes branchof 191), processor 34 identifies a number of counts (C_(interior)) inthe interior portion of the biological growth plate, e.g., interiorportion 187 (192). Also, processor 34 identifies a number of counts(C_(perimeter)) in the perimeter portion of the biological growth plate,e.g., perimeter portion 189 (193). If the number of counts(C_(perimeter)) in the perimeter portion is greater than the number ofcounts (C_(interior)) in the interior portion multiplied by a factor (F)(yes branch of 194), then the growth plate is flagged for additionalreview (195). Once flagged, for example, a technician may be alertedthat a manual review should be performed on the flagged growth plate.

The size of the interior portion and the perimeter portion may vary indifferent implantations. Moreover, the factor (F) that is used maydepend on the defined sizes of the interior portion and perimeterportion. In one example, the perimeter portion comprises approximatelythe outermost 25 percent of the growth area of the growth plate and theinterior portion comprises approximately the innermost 75 percent of thegrowth area of the growth plate. In that case, the factor (F) may beapproximately 1.5, although other factors may also be used. The factor(F) is typically a value greater than 1, indicating a disproportionatenumber of counts in the perimeter portion.

The various rules described herein may be applied individually, or inany combination depending on the growth medium being scanned. By way ofexample, a variety of PETRIFILM plates are currently sold by 3M. Theseinclude aerobic count (AC) plates, coliform count (CC) count plates andE. coli count (EC) plates. Different sets of rules may be applied foranalyzing AC, CC and EC plates. Moreover, by identifying the type ofplate in indicia on the given plates, the application of the correctrules may be automated in the biological scanning system.

For AC plates, improved counting results may be obtained by applicationof rule 1, followed by application of rule 3A or rule 3B, followed byapplication of rule 6. For CC plates, improved counting results may beobtained by application of rule 1, followed by application of rule 2A or2B, followed by application of rule 4. For EC plates, improved countingresults may be obtained by application of rule 1, followed byapplication of rule 2A or 2B, followed by application of rule 4,followed by application of rule 5. These examples, however, areexemplary, and application of various other sets of rules, possibly indifferent orders, may be useful in other embodiments.

A number of embodiments of a biological scanning system have beendescribed. In particular, a variety of counting rules have beendescribed that can be used in a biological scanning system to improvethe accuracy of automated counts of biological agents on a biologicalgrowth plate.

Many of the techniques have been described as beingsoftware-implemented. In that case, a computer readable medium storesprocessor executable instructions that embody one or more of the rulesdescribed above. For example, the computer readable medium may compriserandom access memory (RAM), read-only memory (ROM), non-volatile randomaccess memory (NVRAM), electrically erasable programmable read-onlymemory (EEPROM), flash memory, or the like. The computer readable mediummay also comprise a non-volatile memory such as a CD-ROM used to deliverthe software to customers. Also, the computer readable medium maycomprise an electromagnetic carrier wave, e.g., for delivering thesoftware over a network such as the internet.

The same techniques, however, may also be implemented in hardware.Example hardware implementations include implementations within anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), specifically designed hardware components, or anycombination thereof. In addition, one or more of the techniquesdescribed herein may be partially executed in hardware, software orfirmware.

In any case, various modifications may be made without departing fromthe spirit and scope of the invention. For example, one or more of therules described herein may be used with or without other rules andvarious subsets of the rules may be applied in any order, depending onthe desired implementation. These and other embodiments are within thescope of the following claims.

1. A method comprising: receiving one or more images of a biologicalgrowth medium; determining whether a background color value associatedwith the biological growth medium is within a range; and flagging thebiological growth medium for additional review if the background colorvalue is outside the range.
 2. The method of claim 1, wherein thebiological growth medium is a growth plate and flagging the biologicalgrowth medium for additional review comprises flagging the biologicalgrowth medium for review by a technician.
 3. The method of claim 1,wherein the background color value comprises one or more numbersdefining a shade of the biological growth medium and the range is ashade range.
 4. A method comprising: receiving one or more images of abiological growth medium; identifying a first count of biological agentson the biological growth medium; and reducing the first count togenerate a second count when one or more biological agents identified inthe first count are determined to be in close proximity to one or moreother biological agents identified in the first count.
 5. The method ofclaim 4, wherein the biological agents comprise bacterial colonies. 6.The method of claim 5, wherein reducing the first count to generate asecond count comprises attributing only one count to two or morebacterial colonies within a defined distance of one another.
 7. Themethod of claim 5, wherein reducing the first count to generate a secondcount comprises attributing only one count to two or more bacterialcolonies when a set of identification marks associated with the two ormore bacterial colonies overlap.
 8. The method of claim 5, the methodfurther comprising identifying one or more spreader colonies, whereinreducing the first count to generate a second count comprises excludingbacterial colonies within a defined distance of one of the spreadercolonies from the second count.
 9. The method of claim 5, the methodfurther comprising identifying one or more spreader colonies, whereinreducing the first count to generate a second count comprises excludingbacterial colonies from the second count that have identification marksthat overlap that of a given one of the spreader colonies.
 10. Themethod of claim 4, further comprising determining whether the firstcount is below a threshold and reducing the first count to generate thesecond count only when the first count is below the threshold.
 11. Amethod comprising: receiving one or more images of a biological growthmedium; identifying a first number of biological agents associated withan interior portion of the biological growth medium; identifying asecond number of biological agents associated with a perimeter portionof the biological growth medium; and excluding from the second numberone or more biological agents within a defined distance from an edge ofa growth area of the growth medium when the first number is less than athreshold.
 12. The method of claim 11, further comprising excluding fromthe second number the one or more biological agents within the defineddistance from the edge of the growth area of the growth medium when thefirst number is less than a threshold only when the one or morebiological agents within the defined distance from the edge define areassmaller than a threshold area.
 13. The method of claim 11, furthercomprising: identifying the first number as first color biologicalagents associated with the interior portion of the biological growthmedium; identifying a third number of second color biological agentsassociated with the interior portion of the biological growth medium;identifying the second number as first color biological agentsassociated with a perimeter portion of the biological growth medium;identifying a fourth number of second color biological agents associatedwith the perimeter portion of the biological growth medium; excludingfrom the second number of first color biological agents one or morefirst color biological agents within the defined distance from the edgeof the growth area of the growth medium when the first number of thefirst color biological agents is less than the threshold and the one ormore first color biological agents within the defined distance defineareas smaller than a threshold area; and excluding from the fourthnumber of second color biological agents one or more second colorbiological agents within the defined distance from the edge of thegrowth area of the growth medium when the third number of the secondcolor biological agents is less than the threshold and the one or moresecond color biological agents within the defined distance define areassmaller than the threshold area.
 14. The method of claim 13, wherein thebiological agents comprise bacterial colonies and wherein the firstcolor comprises red and the second color comprises blue.
 15. The methodof claim 11, wherein the interior portion comprises approximately 75percent of the growth area of the growth medium and the perimeterportion comprises approximately 25 percent of the growth area of thegrowth medium.
 16. A method comprising: receiving one or more images ofa biological growth medium; identifying a number of first colorbiological agents associated with an interior portion of the biologicalgrowth medium; identifying a number of second color biological agentsassociated with the interior portion of the biological growth medium;identifying a number of first color biological agents associated with aperimeter portion of the biological growth medium; identifying a numberof second color biological agents associated with the perimeter portionof the biological growth medium; changing the a number of second colorbiological agents associated with the perimeter portion to be includedin the number of first color biological agents associated with theperimeter portion when the number of first color biological agentsassociated with the interior portion is greater than a first thresholdand the number of second color biological agents associated with theinterior portion is less than a second threshold.
 17. The method ofclaim 16, wherein the biological agents comprise bacterial colonies andwherein the first color comprises red and the second color comprisesblue.
 18. The method of claim 16, wherein the interior portion comprisesapproximately 75 percent of a growth area of the growth medium and theperimeter portion comprise approximately 25 percent of the growth areaof the growth medium.
 19. A method comprising: receiving one or moreimages of a biological growth medium; identifying a first number ofbiological agents associated with an interior portion of the biologicalgrowth medium; identifying a second number biological agents associatedwith a perimeter portion of the biological growth medium; and flaggingthe biological growth medium for additional review if the second numberis greater than a factor multiplied by the first number.
 20. The methodof claim 19, wherein the factor is approximately 1.5.
 21. The method ofclaim 19, wherein the biological growth medium is a Petri plate, thebiological agents comprise bacterial colonies and flagging thebiological growth medium for additional review comprises flagging thebiological growth medium for review by a technician.
 22. The method ofclaim 19, wherein the interior portion comprises approximately 75percent of a growth area of the growth medium and the perimeter portioncomprise approximately 25 percent of the growth area of the growthmedium.
 23. A computer readable medium comprising computer readableinstructions that when executed in a processor: receive one or moreimages of a biological growth medium; determine whether a backgroundcolor value associated with the biological growth medium is within arange; and flag the biological growth medium for additional review ifthe background color value is outside the range.
 24. The computerreadable medium of claim 23, wherein the biological growth medium is agrowth plate and the instructions flag the biological growth medium forreview by a technician if the background color value is outside therange.
 25. The computer readable medium of claim 23, wherein thebackground color value comprises one or more numbers defining a shade ofthe biological growth medium and the range is a shade range.
 26. Acomputer readable medium comprising computer readable instructions thatwhen executed in a processor: receive one or more images of a biologicalgrowth medium; identify a first count of biological agents on thebiological growth medium; and reduce the first count to generate asecond count when one or more biological agents identified in the firstcount are determined to be in close proximity to one or more otherbiological agents identified in the first count.
 27. The computerreadable medium of claim 26, wherein the biological agents comprisebacterial colonies.
 28. The computer readable medium of claim 27,wherein reducing the first count to generate a second count comprisesattributing only one count to two or more bacterial colonies within adefined distance of one another.
 29. The computer readable medium ofclaim 27, wherein reducing the first count to generate a second countcomprises attributing only one count to two or more bacterial colonieswhen a set of identification marks associated with the two or morebacterial colonies overlap.
 30. The computer readable medium of claim27, wherein the instructions when executed identify one or more spreadercolonies, wherein reducing the first count to generate a second countcomprises excluding bacterial colonies within a defined distance of oneof the spreader colonies from the second count.
 31. The computerreadable medium of claim 27, wherein the instructions when executedidentify one or more spreader colonies, wherein reducing the first countto generate a second count comprises excluding bacterial colonies fromthe second count that have identification marks that overlap that of agiven one of the spreader colonies.
 32. The computer readable medium ofclaim 26, wherein the instructions when executed determine whether thefirst count is below a threshold and reduce the first count to generatethe second count only when the first count is below the threshold.
 33. Acomputer readable medium comprising computer readable instructions thatwhen executed in a processor: receive one or more images of a biologicalgrowth medium; identify a first number of biological agents associatedwith an interior portion of the biological growth medium; identify asecond number of biological agents associated with a perimeter portionof the biological growth medium; and exclude from the second number oneor more biological agents within a defined distance from an edge of agrowth area of the growth medium when the first number is less than athreshold.
 34. The computer readable medium of claim 33, wherein theinstructions when executed exclude from the second number the one ormore biological agents within the defined distance from the edge of thegrowth area of the growth medium when the first number is less than athreshold only when the one or more biological agents within the defineddistance from the edge define areas smaller than a threshold area. 35.The computer readable medium of claim 33, wherein the instructions whenexecuted: identify the first number as first color biological agentsassociated with the interior portion of the biological growth medium;identify a third number of second color biological agents associatedwith the interior portion of the biological growth medium; identify thesecond number as first color biological agents associated with aperimeter portion of the biological growth medium; identify a fourthnumber of second color biological agents associated with the perimeterportion of the biological growth medium; exclude from the second numberof first color biological agents one or more first color biologicalagents within the defined distance from the edge of the growth area ofthe growth medium when the first number of the first color biologicalagents is less than the threshold and the one or more first colorbiological agents within the defined distance define areas smaller thana threshold area; and exclude from the fourth number of second colorbiological agents one or more second color biological agents within thedefined distance from the edge of the growth area of the growth mediumwhen the third number of the second color biological agents is less thanthe threshold and the one or more second color biological agents withinthe defined distance define areas smaller than the threshold area. 36.The computer readable medium of claim 35, wherein the biological agentscomprise bacterial colonies and wherein the first color comprises redand the second color comprises blue.
 37. The computer readable medium ofclaim 35, wherein the interior portion comprises approximately 75percent of the growth area of the growth medium and the perimeterportion comprises approximately 25 percent of the growth area of thegrowth medium.
 38. A computer readable medium comprising computerreadable instructions that when executed in a processor: receive one ormore images of a biological growth medium; identify a number of firstcolor biological agents associated with an interior portion of thebiological growth medium; identify a number of second color biologicalagents associated with the interior portion of the biological growthmedium; identify a number of first color biological agents associatedwith a perimeter portion of the biological growth medium; identify anumber of second color biological agents associated with the perimeterportion of the biological growth medium; change the a number of secondcolor biological agents associated with the perimeter portion to beincluded in the number of first color biological agents associated withthe perimeter portion when the number of first color biological agentsassociated with the interior portion is greater than a first thresholdand the number of second color biological agents associated with theinterior portion is less than a second threshold.
 39. The computerreadable medium of claim 38, wherein the biological agents comprisebacterial colonies and wherein the first color comprises red and thesecond color comprises blue.
 40. The computer readable medium of claim38, wherein the interior portion comprises approximately 75 percent of agrowth area of the growth medium and the perimeter portion compriseapproximately 25 percent of the growth area of the growth medium.
 41. Acomputer readable medium comprising computer readable instructions thatwhen executed in a processor: receive one or more images of a biologicalgrowth medium; identify a first number of biological agents associatedwith an interior portion of the biological growth medium; identify asecond number biological agents associated with a perimeter portion ofthe biological growth medium; and flag the biological growth medium foradditional review if the second number is greater than a factormultiplied by the first number.
 42. The computer readable medium ofclaim 41, wherein the factor is approximately 1.5.
 43. The computerreadable medium of claim 41, wherein the biological growth medium is aPetri plate, the biological agents comprise bacterial colonies and theinstructions when executed flag the biological growth medium for reviewby a technician if first number is greater than a factor multiplied bythe second number.
 44. The computer readable medium of claim 41, whereinthe interior portion comprises approximately 75 percent of a growth areaof the growth medium and the perimeter portion comprise approximately 25percent of the growth area of the growth medium.
 45. A systemcomprising: an imaging device to generate one or more images of abiological growth medium; and a processor to receive the images,determine whether a background color value associated with thebiological growth medium is within a range, and flag the biologicalgrowth medium for additional review if the background color value isoutside the range.
 46. The system of claim 45, wherein the backgroundcolor value comprises one or more numbers defining a shade of thebiological growth medium and the range is a shade range.
 47. A systemcomprising: an imaging device to generate one or more images of abiological growth medium; and a processor to receive the images,identify a first count of biological agents on the biological growthmedium, and reduce the first count to generate a second count when oneor more biological agents identified in the first count are determinedto be in close proximity to one or more other biological agentsidentified in the first count.
 48. The system of claim 47, wherein thebiological agents comprise bacterial colonies.
 49. The system of claim48, wherein the processor reduces the first count to generate a secondcount by attributing only one count to two or more bacterial colonieswithin a defined distance of one another.
 50. The system of claim 48,wherein the processor reduces the first count to generate a second countby attributing only one count to two or more bacterial colonies when aset of identification marks associated with the two or more bacterialcolonies overlap.
 51. The system of claim 48, wherein the processoridentifies one or more spreader colonies, wherein the processor reducesthe first count to generate a second count by excluding bacterialcolonies within a defined distance of one of the spreader colonies fromthe second count.
 52. The system of claim 48, wherein the processoridentifies one or more spreader colonies, wherein the processor reducesthe first count to generate a second count by excluding bacterialcolonies from the second count that have identification marks thatoverlap that of a given one of the spreader colonies.
 53. The system ofclaim 47, wherein the processor determines whether the first count isbelow a threshold and reduces the first count to generate the secondcount only when the first count is below the threshold.
 54. A systemcomprising: an imaging device to generate one or more images of abiological growth medium; and a processor to receive the images,identify a first number of biological agents associated with an interiorportion of the biological growth medium, identify a second number ofbiological agents associated with a perimeter portion of the biologicalgrowth medium, and exclude from the second number one or more biologicalagents within a defined distance from an edge of a growth area of thegrowth medium when the first number is less than a threshold.
 55. Thesystem of claim 54, wherein the processor, excludes from the secondnumber the one or more biological agents within the defined distancefrom the edge of the growth area of the growth medium when the firstnumber is less than a threshold only when the one or more biologicalagents within the defined distance from the edge define areas smallerthan a threshold area.
 56. The system of claim 54, wherein the processoridentifies the first number as first color biological agents associatedwith the interior portion of the biological growth medium, identifies athird number of second color biological agents associated with theinterior portion of the biological growth mediums identifies the secondnumber as first color biological agents associated with a perimeterportion of the biological growth medium, identifies a fourth number ofsecond color biological agents associated with the perimeter portion ofthe biological growth medium, excludes from the second number of firstcolor biological agents one or more first color biological agents withinthe defined distance from the edge of the growth area of the growthmedium when the first number of the first color biological agents isless than the threshold and the one or more first color biologicalagents within the defined distance define areas smaller than a thresholdarea, and excludes from the fourth number of second color biologicalagents one or more second color biological agents within the defineddistance from the edge of the growth area of the growth medium when thethird number of the second color biological agents is less than thethreshold and the one or more second color biological agents within thedefined distance define areas smaller than the threshold area.
 57. Thesystem of claim 54, wherein the interior portion comprises approximately75 percent of the growth area of the growth medium and the perimeterportion comprises approximately 25 percent of the growth area of thegrowth medium.
 58. A system comprising: an imaging device to generateone or more images of a biological growth medium; and a processor toreceive the images, identify a number of first color biological agentsassociated with an interior portion of the biological growth medium,identify a number of second color biological agents associated with theinterior portion of the biological growth medium, identify a number offirst color biological agents associated with a perimeter portion of thebiological growth medium, identify a number of second color biologicalagents associated with the perimeter portion of the biological growthmedium, and change the a number of second color biological agentsassociated with the perimeter portion to be included in the number offirst color biological agents associated with the perimeter portion whenthe number of first color biological agents associated with the interiorportion is greater than a first threshold and the number of second colorbiological agents associated with the interior portion is less than asecond threshold.
 59. The system of claim 58, wherein the biologicalagents comprise bacterial colonies and wherein the first color comprisesred and the second color comprises blue and, wherein the interiorportion comprises approximately 75 percent of a growth area of thegrowth medium and the perimeter portion comprise approximately 25percent of the growth area of the growth medium.
 60. A systemcomprising: an imaging device to generate one or more images of abiological growth medium; and a processor to receive the images,identify a first number of biological agents associated with an interiorportion of the biological growth medium, identify a second numberbiological agents associated with a perimeter portion of the biologicalgrowth medium, and flag the biological growth medium for additionalreview if the second number is greater than a factor multiplied by thefirst number.
 61. The system of claim 60, wherein the factor isapproximately 1.5, the interior portion comprises approximately 75percent of a growth area of the growth medium and the perimeter portioncomprise approximately 25 percent of the growth area of the growthmedium.